Radioactive Waste

Photo by: Thomas Bethge

Radioactive waste (or nuclear waste) is a material deemed no longer useful
that has been contaminated by or contains radionuclides. Radionuclides are
unstable atoms of an element that decay, or disintegrate spontaneously,
emitting energy in the form of radiation. Radioactive waste has been
created by humans as a by-product of various endeavors since the discovery
of radioactivity in 1896 by Antoine Henri Becquerel. Since World War II,
radioactive waste has been created by military weapons production and
testing; mining; electrical power generation; medical diagnosis and
treatment; consumer product development, manufacturing, and treatment;
biological and chemical research; and other industrial uses.

There are approximately five thousand natural and artificial radionuclides
that have been identified, each with a different half-life. A half-life is
a measure of time required for an amount of radioactive material to
decrease by one-half of its initial amount. Half-life values for each
known radionuclide are unique. The half-life of a radionuclide can vary
from fractions of a second to millions of years. Some examples of
radionuclides with a range of different half-lives include sodium-26
(half-life of 1.07 seconds), hydrogen-3 (half-life of 12.3 years),
carbon-14 (half-life of 5,730 years), and uranium-238 (half-life of 4.47
billion years). The decay process of a radionuclide is the

Workers at a nuclear power plant standing near a storage pond filled
with spent fuel. (

mechanism by which it spontaneously releases its excess energy. Typical
mechanisms for radioactive decay are alpha, beta, and gamma emission.
Alpha decay is a process that is usually associated with heavy atoms, such
as uranium-238 and thorium-234, where excess energy is given off with the
ejection of two neutrons and two protons from the nucleus. Beta decay
involves the ejection of a beta particle, which is the same as an
electron, from the nucleus of an excited atom. A common example of a
beta-emitter found in radioactive waste is strontium-90. After an alpha or
beta decay, the nucleus of an atom is often in an excited state and still
has excess energy. Rather than releasing this energy by alpha or beta
decay, energy is lost by gamma emission—a pulse of electromagnetic
radiation from the nucleus of an atom.

Everything on Earth is exposed to radiation. However, exposure to
radiation at levels greater than natural background radiation can be
hazardous.
Exposure to certain high levels of radiation, such as that from
high-level radioactive waste, can even cause death. Radiation exposure can
also cause cancer, birth defects, and other abnormalities, depending on
the time of exposure, amount of radiation, and the decay mechanism.
High-level radioactive waste from nuclear reactors can be hazardous for
thousands of years. Radioactive waste can be categorized by its source or
point of origin. Because of this, the governments of many nations have
developed waste classification systems to regulate the management of
radioactive waste within their borders. The proper treatment, storage, and
disposal of radioactive waste are prescribed based on the waste
classification system defined in a nation's laws, rules, and
regulations. The table outlines common categories of radioactive waste.

Radioactive Waste Description

Radioactive waste can vary greatly in its physical and chemical form. It
can be a solid, liquid, gas, or even something in between, such as sludge.
Any given radioactive waste can be primarily water, soil, paper, plastic,
metal, ash, glass, ceramic, or a mixture of many different physical forms.
The chemical form of radioactive waste can vary as well. Radioactive waste
can contain radionuclides of very light elements, such as radioactive
hydrogen (tritium), or of very heavy elements, such as uranium.
Radioactive waste is classified as high, intermediate, or low level.
Depending on the radionuclides contained in it, a waste can remain
radioactive from seconds to minutes, or even for millions of years.

Radioactive Waste Management

Radioactive waste management includes the possession, transportation,
handling, storage, and ultimate disposal of waste. The safe management of
radioactive waste is necessary to protect public health. If handled
improperly, potential exposures of humans to high-level radioactive waste
can be dangerous, even deadly. Some radioactive wastes such as certain
types of
transuranic waste
can cause biological effects in humans only if the radionuclides
contained in the waste are directly inhaled or ingested. Most low-level
radioactive wastes can be handled by humans without any measurable
biological effects. Nevertheless, good handling practices of all
radioactive materials and waste should be the goal to provide optimum
protection to humans and the environment. There have been historic
practices associated with the use of radioactive material where workers
were unaware of potential risks. The radium watch dial painters of the
1920s illustrate the health effects that can be associated with improper
handling practices. The painters experienced high occurrences of cancer of
the larynx and tongue due to ingestion of radium.

The transportation of radioactive waste can occur via roadway, aircraft,
ship/barge, and rail. The classification and physical size of radioactive
waste dictate the method of transport, the packaging required, and the
labeling necessary to allow for the shipment of a specific waste. There
are international transportation requirements for radioactive waste, as
well as more specific regulations in individual countries.

Radioactive Waste Disposal

Various methods to manage and dispose of radioactive waste have been
considered. Proposed management and disposal methods have included the

COMMON CATEGORIES OF RADIOACTIVE WASTE

Waste Category

Description of Waste Category

Common Sources of Waste

Common Radionuclides in Waste and Their Half-Life (y=years)

High-Level Radioactive Waste

Highly radioactive material that is deemed a waste that requires
special precautions by humans, including remote handling and use
of shielding; also includes spent fuel and waste resulting from
the reprocessing of used fuel

Partially used fuel from nuclear power reactors; liquid waste from
the reprocessing of spent fuel taking place outside the United
States

strontium-90 half-life: 29.78 y
cesium-137 half-life: 30.07 y

Transuranic Waste

Material that is deemed a waste that contains radionuclides with
an atomic number greater than that of uranium (92)

Weapons-production waste included mixed transuranic waste

plutonium-238 half-life: 87.7 y
americium-241 half-life: 432.7 y

Mixed Waste

Material that is deemed a waste that contains both radionuclides
and a characteristic or listed hazardous waste

Weapons-production waste and some research wastes

plutonium-239 half-life: 24,100 y
plutonium-241 half-life: 14.4 y

Naturally Occurring Radioactive Material (NORM) Waste

Material that is deemed a waste that contains radionuclides that
are present on Earth without any human interaction

Scale buildup on pipe walls that carry petroleum products

radium-226 half-life: 1,599 y
radium-228 half-life: 5.76 y

Uranium or Thorium Mill Tailings Waste

The tailings material created as a by-product by the extraction of
uranium or thorium from natural ore formations

Production exclusively at the site of milling for rare earth
extraction

Material that is deemed a waste that generally has been
contaminated by or contains short-lived radionuclides or
longer-lived radionuclides in relatively low concentrations.
Low-level radioactive waste is further segregated into classes
(see below)

Industrial trash from nuclear power plants; medical, research, and
academic trash such as paper, plastic, and glass

hydrogen-3 half-life:12.32 y
cobalt-60 half-life: 5.27 y

Class A:

Lowest level of LLRW, generally decays in 100 y

Class B:

Moderate level of LLRW, generally decay in 300 y

Class C:

Special controls required for this high level of LLRW, including
shielding/barriers that must isolate for 500 y

Greater than Class C:

Exceed the Class C limits and cannot be disposed in LLRW
facilities; must be disposed with high-level radioactive waste

Exempt Material or Very Low Activity Waste

Material that is deemed a waste that contains trace concentrations
of short half-life radionuclides that are considered below
regulatory concern

Most of the civilian high-level radioactive waste throughout the world is
currently being stored at nuclear power reactor sites. The spent nuclear
fuel generated from the 103 operating civilian power reactors in the
United
States is currently being stored on-site at the point of generation. In
Europe, prior to on-site storage, spent fuel is first sent to either the
Sellafield site in the United Kingdom or the La Hague site in France to be
reprocessed in order to recover usable fuel. No reprocessing of commercial
spent fuel is being conducted in the United States. In the United States,
spent fuel and other high-level radioactive waste awaits the construction
of a central, permanent repository. It is currently stored in spent fuel
pools or, in some cases, in dry casks. Spent fuel pools are water-filled,
lead-lined chambers that are adjacent to reactors on civilian power
reactor sites. Dry-cask storage has become necessary in some cases where
the on-site spent fuel pools have reached capacity. The Office of Civilian
Radioactive Waste Management at the U.S. Department of Energy (DOE) is
charged with developing this federal repository. Amid local opposition,
Yucca Mountain, Nevada, is presently under study to evaluate its
suitability as a central repository for all U.S. high-level radioactive
waste. The Yucca Mountain site has been officially designated by President
George W. Bush and Congress for full-scale studies. There has been further
emphasis placed on the security of spent fuel, and in general on nuclear
reactor sites following the September 11, 2001, terrorist attacks. Nuclear
reactor sites that store spent fuel have been identified as possible
terrorist targets and, therefore, have been subject to heightened security
and debate over potential vulnerabilities. France, Germany, the United
Kingdom, and Japan also have plans to develop centralized repositories for
high-level radioactive waste at various times in the future.

Transuranic waste generated by the DOE has an operational final
repository. The Waste Isolation Pilot Project located near Carlsbad, New
Mexico, accepts transuranic waste and mixed transuranic waste (i.e.,
transuranic waste that also has a hazardous waste component) from federal
facilities throughout the United States. This facility is comprised of
disposal cavities mined into a salt formation some 2,150 feet underground.

The disposal method used in the 1960s and 1970s for low-level radioactive
waste was shallow land burial in earthen trenches. The infiltration of
water into these trenches resulted in the migration or movement of certain
radionuclides into surrounding soil and groundwater. To respond to such
problems, engineered disposal units have been developed to replace shallow
land burial, utilizing enhanced cover systems to reduce the potential for
water infiltration. The trial-and-error nature of early radioactive waste
disposal sites has rendered new facility development a slow and cautious
process.

Historical Perspective

The first commercial site for the disposal of low-level radioactive waste
was opened in Beatty, Nevada, in 1962. Within the next ten years, five
more sites opened in the United States: in Washington, Illinois, South
Carolina, New York, and Kentucky. Private companies operated these sites
on land leased from state governments. Prior to 1979, the DOE routinely
used commercial sites for the disposal of federal waste.

Migration problems at commercial disposal sites in the United States were
first discovered in the late 1960s. Four of the six commercial low-level
radioactive waste disposal sites in the United States closed. Three of the
four sites that closed developed leaks due to erosion by surface water,
subsidence on tops of trenches, or buried waste immersed in water. Several
of these
locations became federal
Superfund
sites due to radionuclides migrating beyond the disposal trenches,
complicated by the presence of hazardous waste within the same facilities.

The historical problems experienced with commercial radioactive waste
disposal in the United States resulted in the development of new
regulatory requirements for site selection, construction parameters,
operating practices, and waste-acceptance criteria at future disposal
sites. A new U.S. disposal regulation, Title 10, Code of Federal
Regulations, Part 61, "Licensing Requirements for Land Disposal of
Radioactive Wastes" was introduced in 1982. This regulation
outlines the requirements necessary to ensure public health, safety, and
the long-term protection of the environment. Since the development of this
new regulation in the United States, only one site, in Clive, Utah, has
been licensed and opened for disposal of low-level radioactive waste.

Summary

Radioactive waste is being generated in the United States and throughout
the world as a result of research, mining, electricity production, nuclear
weapons production, and medical uses. There are many possible beneficial
activities due to the use of radioactive material. Laws, rules, and
regulations are made on a global scale to help ensure the safe handling of
radioactive waste to protect human and environmental health. However, the
question of the safe final deposition of all radioactive waste generated
worldwide is still problematic.